1. Field of the Invention
This invention relates to compositions that can be used to generate a gas and their use in an air bag inflator.
2. Description of the Prior Art
Conventional automotive air bags inflate quickly after being triggered by a crash sensor, usually located in the front bumper of the automobile. The bag is inflated by the generation of gas from a chemical composition. This composition is usually sodium azide. In a crash, the crash sensors send an electronic signal to a pyrotechnic initiator known as a squib which detonates a first chemical reaction. The flame and heat from this first chemical reaction ignite the sodium azide which in turn produces the inflator gas that blows up the bag.
However, several problems exist in such conventional air bags. Firstly, the chemicals which are contained in the inflator usually include one or more of gun powder, sodium azide, nitroglycerin, boron, potassium nitrate, copper oxide, and hydrochloric acid. Some of these chemicals are poisonous and hazardous. Indeed, the boron present in the inflator, as well as other catalysts, can react with sodium azide to form boron azide. Boron azide is less stable, i.e., more likely to explode, than sodium azide and can thus cause the premature deployment of the air bag. Similarly, the sodium azide can react with metals in contact therewith such as copper-brass to form copper azide. Such metal azides are very explosive and can also lead to the premature deployment of the air bag.
Secondly, the chemical reactions that produce the inflator gas also result in the production of sodium particles and sodium hydroxide particles. These particles, which are produced at a temperature of around 600.degree. C., can pass through the bag and strike the driver, resulting in chemical burns. Further, these particles could cause the bag to burst and thus subject the driver to the hot inflator gas itself.
Finally, the handling and disposal of these air bag inflator compositions is troublesome because many are considered as class A explosives and subject to special federal regulations. Further, the air bag inflator compositions are toxic as are some of the reaction by-products.
Another gas generating composition that has been used in an air bag inflator is a mixture of potassium perchlorate and polyvinylchloride. However, this composition produces toxic chlorine gas upon ignition.